Internally cooled unit injector

ABSTRACT

A unit fuel injector providing cooling of the nozzle by the fuel, with a valve arrangement in the return passage to intermittently stop circulation of the fuel and a check valve in the fuel delivery passage to prevent blow-back of combustion gases during the engine power stroke.

United States Patent 1191 Dreisin 51 June 5,1973

[54] INTERNALLY COOLED UNIT INJECTOR [75] Inventor: Alerrander Dreisin,Olympia Fields,

[73] Assignee: Allis-Chalmers Corporation, Milwaukee, Wis.

[22] Filed: Nov; 18, 1971 [21] Appl. No.: 199,922

[52] US. Cl. ..239/89, 123/139 AK, 239/1325 [51] Int. Cl ..F02m 39/00[58] Field of Search ..239/88, 89, 90, 9| 239/95, 132, 132.1, 132.3,132.5, 533;

[56] References Cited UNITED STATES PATENTS 2,260,077 10/1941Kearney..... ..123/139AK 2,792,259 5/1957 Shallenberg ..l23/l39 AK 73,486,494 l2/l969 Dreisin ..239/89 X 2,559,364 7/1951 Mashinter..l23/139 AK 3,409,225 l [[1968 Maddalozzo et al. ..239l89 PrimaryExaminer-M. Henson Wood, Jr.

Assistant Examiner-Michael Mar Attorney-Arthur L. Nelson, Robert B.Benson and Charles L. Schwab [57] ABSTRACT A unit fuel injectorproviding cooling of the nozzle by the fuel, with a valve arrangement inthe return passage to intermittently stop circulation of the fuel and acheck valve in the fuel delivery passage to prevent blow-back ofcombustion gases during the engine power stroke.

10 Claims, 5 Drawing Figures INTERNALLY COOLED UNIT INJECTOR Thisinvention relates to cooling of a unit fuel injector and moreparticularly to a valve arrangement to prevent blow-back of the highpressure combustion gases from the combustion chamber during the powerstroke.

In the conventional fuel injector using a differential valve in thenozzle, the closing pressure is always lower than the opening pressure.This is due to the fact that when the needle is closed the hydraulicpressure acts only on the differential area between the outside diameterof the conical needle seat and the maximum cylindrical diameter of theneedle. When the needle is open, the hydraulic pressure can act on theentire area corresponding to maximum outside diameter of the needle. Itis the practice when using a differential valve, to adjust the springforce acting on the needle in such a way that the closing pressure ofthe nozzle is several hundred pounds per square inch higher than themaximum pressure developed during the combustion process in the enginecylinder. This condition is required to prevent the combustion gasesfrom penetrating into the interior of the injector after the opening ofthe spill port and before the needle is seated. If this condition is notmet, even a small quantity of high pressure gas, which can penetrateinto the interior of the injector, will expand a hundredfold duringsubsequent relief of the pressure down to the values of the supplypressure and may prevent proper filling of the pump chamber preparatoryto the subsequent injection. There is also the possibility of combustiongases penetrating into the interior of the injector after seating of theneedle. This possibility may be created by an imperfect seating of theneedle in the nozzle body. It is especially important to guard againstthe penetration of the combustion gases into the interior of theinjector during the initial portion of the engine power stroke while theengine cylinder pressures are high. Accordingly, this invention isintended to overcome this problem.

It is an object of this invention to provide a cooling system for a unitfuel injector having a valve arrangement to prevent blow-back of thecombustion gases from the internal combustion chamber during the powerstroke of the engine.

It is a further object of this invention to provide a fuel cooling meansfor cooling a unit injector including a check valve between thecombustion chamber and the high pressure fuel injection pumping chamber,and a port between the combustion chamber and the return passage whichare closed during the power stroke of the engine to prevent blow-back ofgases into the differential valve chamber.

The objects of this invention are accomplished by a fuel cooling systemwhich supplies cooling fuel to the unit injector. The supply passagesupplies fuel to the high pressure fuel injection pumping chamber. Fuelis delivered from the chamber through a check valve as it passes to thedifferential valve in the nozzle. The cooling fuel passes through thedifferential valve chamber and is returned through a return passage tothe fuel supply tank. The fuel intermittently flows through differentialvalve chamber in the fuel injection nozzle for cooling during the phaseof the cycle in which there is no fuel injection.

During the fuel injection phase of the cycle, the check valve is openand the high pressure fuel from the high pressure fuel injection pumpingchamber passes through the check valve and through the differentialvalve. Fuel injection is initiated when a predetermined pressure isreached and the differential valve opens. Fuel injection is terminatedwhen the spill port registers with the upper edge of the pumping land onthe plunger and the pressure is relieved from the high pressure pumpingchamber. The cross passage on the plunger is closed so no fuel ispermitted to return through the return passage for substantially all ofthe power stroke. With the return passage closed and the check valveclosed, the pressure build-up in the combustion cham-' ber which tendsto open the differential valve is counteracted since no movement of fuelfrom the differential valve chamber is permitted. Accordingly, blowbackinto the differential valve is prevented.

Referring to the drawings, the preferred embodiment of this invention isillustrated.

FIG. 1 is a cross section view taken on line I-I of FIG. 2.

FIG. 2 is a cross section view taken on line 11-11 of FIG. 1. v

FIG. 3 is an enlarged cross section view taken on line III-Ill of FIG.1.

FIG. 4 is a schematic illustration of the fuel injection pump and a fuelsupply system.

FIG. 5 illustrates the timing of fuel injection and opening and closingof the cooling annulus on the plunger.

Referring to FIG. 1, a fuel pump in unit injector l is shown. The unitinjector includes the housing 2 receiving a plunger 3 connected to thecam follower 4. The cam follower 4 is biased to the extended position bythe follower spring 5, and reciprocates within the housing 2 in responseto a cam on an engine driven camshaft 45.

The unit injector housing 2 defines an inlet passage 6 and an outletpassage 7. The inlet passage 6 is connected to the supply pump 44 andthe outlet passage 7 is connected through a return conduit 55 to thefuel tank to return fuel which operates as the cooling fluid for coolingthe unit fuel injector. The housing 2 houses the barrel 8 which receivesthe plunger 3 which forms the pumping land 9 and cooling control land10.'The land 10 forms annular groove or annulus 11 forming cross passagefor return flow of fuel. The land 9 on the plunger 3 initiates fuelinjection when the leading heli-'v cal edge 12 closes the port 13. Thetrailing helical edge 14 terminates fuel injection when it registerswith the port 15 as the plunger advances in the high pressure chamber16.

The upper spring retainer 17 forms the lower surface of the highpressure chamber 16 and the passage 18 leads from the high pressurechamber into the passage 19 in the lower spring retainer 20-. The nozzle21 forms a valve chamber 22 which receives the check valve 23. Thepassage 24 supplies fuel to the differential valve chamber 25. Thedifferential valve includes the needle 26 seated on the conical seat 27.The check valve 23 is located close to the differential valve 30 and issensitive to reverse fuel movement from the differential valve chamber.The orifices 28 delivers fuel to the combustion chamber.

When the fuel injection pump is not injecting fuel, the differentialvalve 30 is closed and fuel is returned to the passage 29 in the nozzle21. Passage 29 is in communication with passages 31 and 32 in the lowerspring retainer 20 and the upper spring retainer 17. These passages arein turn connected through the return passage 33, the annular groove 11,and passage 35 to the outlet passage 7. The inlet passage 6 is connectedto the supply passage 36 which is in communication with the highpressure fuel injection chamber 16, during the phase of cam at which theport 13 is not covered.

Referring to FIG. 2, the inlet passage 36 is shown connected to theinlet port 13. Port 13 is closed to provide fuel injection. The returnport 38 is also closed during fuel injection and opens to terminate fuelinjection through the return passage 35.

Referring to FIG. 3, it illustrates a section view of the upper portionof the nozzle 21 and the check valve 23. The needle 25 is normallybiased to a closed position by the spring 40 as shown in FIG. 1. Thespring is compressively positioned under the upper spring retainer 17and engages on its underside the spring seat 42.

Referring to FIG. 4, the engine 43 drives the fuel supply pump 44 andthe camshaft 45. The camshaft 45 has a plurality of cams 46, 47, 48 and49 for driving the cam followers of the fuel injectors 50, 51, 52 and53. The pump 44 pumps fuel into the supply conduit 54 which is connectedby parallel conduits to each of the fuel injectors 50, 51, 52 and 53.The return conduit 55 returns fuel through the check valve 56 to thefuel tank 57 for cooling of the unit fuel injector. The flow of coolingfuel from each of the fuel injectors is interrupted during fuelinjection.

FIG. illustrates a graph showing the sequence of operation of the fuelinjector responsive to cam rotation. The angle of cam rotation showsthat the annulus or annular groove 11 formed on land of the plunger 3closes the cross passage for fuel return prior to fuel injection whichis slightly beyond 20 of cam rotation. Fuel injection initiates atapproximately 30 of cam rotation and terminates slightly beyond 40 ofcam rotation and before top dead center. The cam retains the annulargroove or annulus l1 closed through the power stroke of the engine. Theannulus opening registers at approximately 140 of cam rotation forproviding cross passage between return passage 33 and 35 at which timethe pressure in the combustion chamber is so low .that it is incapableof opening the differential valve.

FIG. 5 illustrates the cycle for any cylinder and the cam operation forfuel injection in its mating combustion chamber.

The operation of the unit fuel injector will be described in thefollowing paragraphs.

The unit injector shown in the drawings is provided with a coolingcircuit which allows supply fuel to flow around the nozzle tip duringthe time interval between fuel injections. The supply fuel from thesupply pump 44 is maintained at a low pressure which may be in thevicinity of 10-40 pounds per square inch. It enters through the inletpassage 6 flowing through the supply passage 36. Normally the plunger ofthe fuel injector is in the position as shown in FIG. 1 when the camfollower is operating on the base circle of the cam. It is understoodthat cam lift or rise refers to a condition where the cam lobe on thecamshaft causes the cam follower to move away from the base circlealthough this may be indicated as a downward movement in FIG. 1.Likewise when spring 5 returns the cam follower 4 to the base circle,the cam follower is considered to fall in response to the biasing forceof the spring 5.

The inlet port 6 is connected to the pump and allows fuel to enter intothe pumping chamber 16 through the inlet passage 36 and port 13. Thefuel flows through the high pressure pumping chamber 16, the passages18, 19, and 24 and check valve 23 to the differential valve chamber 25.When the fuel injector is not injecting fuel, the fuel is allowed toreturn through the passages 29, 31, 32 and annular groove 11 and returnpassage 35 to the outlet passage 7. i

Fuel has free-flow from the high pressure fuel injection chamber 16through the check valve 23 to the differential valve chamber 25. Thecheck valve prevents any return flow from the differential valve chamber25.

FIG. 4 illustrates the unit fuel injectors on the engine which areconnected in parallel to the fuel supply line and in turn the fueloutlets are connected in parallel to the fuel drain manifold equippedwith a pressure relief valve 56, the downstream side of which leads tothe fuel tank 57.

Because of the flow resistance of the internal passages in the unit fuelinjectors there is always a pressure drop between the fuel inlet and thefuel outlet. The barrel is fitted snuggly in the counterbore in theinjection nozzle housing 2 so that outside of negligible leakage themain quality of supply fuel flow has to move through the injector asdescribed above.

When the engine piston is on its compression stroke, the injectionplunger begins its movement responsive to injector cam lift. At theapproximate point in time which may be approximately 20 to 30 degreesbefore engine top dead center, the annular groove 11 will over-ride thecross passages of the return passages 33 and 35, thereby interruptingthe flow cooling fluid. As the plunger continues to lift, the leadinghelical edge 12 will be advanced sufficiently to close the inlet port13, trapping fuel in the pumping chamber. This commences fuel injection.Fuel pressure in the injector builds up until it exceeds the openingpressure of the differential valve 30, and then the needle 26 opensinjecting fuel into the cylinder. This continues until the trailinghelical edge 14 registers with the spill port 15. The plunger proceedstoward the top of the cam lift, leaving the spill port open. Theinjection pressure in the injector starts falling after the opening ofthe spill port and as it decays to the value of the nozzle closingpressure, the needle starts falling back towards its seat. When thedifferential valve is completely closed, fuel flow from the highpressure chamber 16 through check valve 23 stops. Any tendency of returnflow through the check valve 23 will immediately close the check valve23. The annular groove 11 still remains out of registry with the crosspassages between return passages 33 and 35. Accordingly, the inlet andoutlet fuel passages communicating with the differential valve chamberare closed. Consequently, any possibility of blow-back into thedifferential valve is eliminated. The annular groove 1 1 remains out ofregistry with the cross passages 33 aand 35 for substantially all of thepower stroke. It is noted on the graph in FIG. 5 that the termination ofthe power stroke at bottom dead center is approximately the same pointin the cycle that the cooling annulus opens. When the cooling annulus 11opens and supply fuel is permitted to pass through the cooling annulus,the pressure in the combustion chamber is reduced to a value where thereis no longer any danger of blow-back of combustion gases into thedifferential valve.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A unit fuel injector having fuel cooling means comprising a fuelinjector housing defining an inlet passage and an outlet passage, aplunger reciprocating in said housing and defining a fuel injectionpumping chamber with said inlet passage intermittently communicatingwith said pumping chamber, means defining an injection nozzle adaptedfor injecting fuel in a combustion chamber, means defining supplypassage means connected between said injection pumping chamber and saidinjection nozzle, a differential valve in said injection nozzle, a checkvalve positioned in said supply passage means adjacent said differentialvalve, return passage means connected between said differential valveand said outlet passage through said plunger, said plunger defining apassage providing port means in said return passage means to selectivelyclose said return passage means during fuel injection, said check valveand said port means on said plunger operating as means for trapping fuelin said differential valve chamber to prevent high pressure gases fromentering said differential valve from the combustion chamber.

2. A unit fuel injector having fuel cooling means as set forth in claim1 wherein said check valve defines a pressure sensitive valve elementpermitting unidirectional flow of hydraulic fuel from said fuelinjection chamber to said differential valve.

3. A unit fuel injector having fuel cooling means as set forth in claim1 wherein said port means on said plunger defines an annular groove,said annular groove normally opening said return passage means forconnection to a drain manifold of the fuel injection system.

4. A unit fuel injector having fuel cooling means as set forth in claim1 wherein said plunger defines a land for initiating and terminatingfuel injection upon register with said inlet passage means and saidoutlet passage means when said plunger is reciprocated, a cooling landdefining said port means as an annular groove normally opening saidreturn passage means to provide flow of cooling fluid through saidreturn passage when said fuel injector is not injecting fuel.

5. A unit fuel injector having fuel cooling means as set forth in claim1 wherein said nozzle defines a differential valve chamber, saiddifferential valve positioned in said differential valve chamber, meansconnecting said supply passage means and said return passage means tosaid valve chamber for circulating fuel for cooling said nozzle.

6. A unit fuel injector having fuel cooling means as set forth in claim1 wherein said nozzle includes a differential valve, a check valve insaid nozzle adjacent said differential valve to increase sensitivity toreturn flow from said differential valve to said high pressure chamber.

7. A unit fuel injector having fuel cooling means as set forth in claim1 including a cam driven by said engine, a cam follower operating inresponse to rotation of said cam for operating said plunger, said camdefining a cam lobe for driving said plunger to close said port meansprior to initiation of the power stroke of the engine and open said portmeans substantially at the end of the power stroke.

8. A unit fuel injector having a fuel cooling means as set forth inclaim 1 including a cam, means for driving said cam, a cam followerengaging said cam and connected to said plunger, said cam driving saidcam follower and said plunger to initiate and terminate fuel injectionon the rising portion of said cam with a sufficient dwell formaintaining the port means in a closed position during the greaterportion of the power stroke of the corresponding cylinder.

9. A unit fuel injector having a fuel cooling means as set forth inclaim 1 wherein said plunger includes a pumping land on said plunger forinitiation and termination of fuel injection upon closing of said inletport and opening of said return port respectively, a cam for drivingsaid cam, a cam follower driven by said cam driving said plunger, saidcam defining a lobe for lifting said cam follower and said plunger tomaintain the port means in the closed position for substantially 90 ofcam rotation.

10. A unit fuel injector having a fuel cooling means as set forth inclaim 1 wherein said plunger includes a land defining initiation andtermination of fuel injection upon closing of an inlet port with saidhigh compression chamber and opening of an outlet port with said highpressure chamber, a second land on said plunger defining said port, acam defining a lobe having a dwell of substantially whereby said camfollower maintains said return passage means in a closed position fortrapping fuel in said differential valve chamber to prevent blow-back insaid differential chamber.

1. A unit fuel injector having fuel cooling means comprising a fuelinjector housing defining an inlet passage and an outlet passage, aplunger reciprocating in said housing and defining a fuel injectionpumping chamber with said inlet passage intermittently communicatingwith said pumping chamber, means defining an injection nozzle adaptedfor injecting fuel in a combustion chamber, means defining supplypassage means connected between said injection pumping chamber and saidinjection nozzle, a differential valve in said injection nozzle, a checkvalve positioned in said supply passage means adjacent said differentialvalve, return passage means connected between said differential valveand said outlet passage through said plunger, said plunger defining apassage providing port means in said return passage means to selectivelyclose said return passage means during fuel injection, said check valveand said port means on said plunger operating as means for trapping fuelin said differential valve chamber to prevent high pressure gases fromentering said differential valve from the combustion chamber.
 2. A unitfuel injector having fuel cooling meanS as set forth in claim 1 whereinsaid check valve defines a pressure sensitive valve element permittingunidirectional flow of hydraulic fuel from said fuel injection chamberto said differential valve.
 3. A unit fuel injector having fuel coolingmeans as set forth in claim 1 wherein said port means on said plungerdefines an annular groove, said annular groove normally opening saidreturn passage means for connection to a drain manifold of the fuelinjection system.
 4. A unit fuel injector having fuel cooling means asset forth in claim 1 wherein said plunger defines a land for initiatingand terminating fuel injection upon register with said inlet passagemeans and said outlet passage means when said plunger is reciprocated, acooling land defining said port means as an annular groove normallyopening said return passage means to provide flow of cooling fluidthrough said return passage when said fuel injector is not injectingfuel.
 5. A unit fuel injector having fuel cooling means as set forth inclaim 1 wherein said nozzle defines a differential valve chamber, saiddifferential valve positioned in said differential valve chamber, meansconnecting said supply passage means and said return passage means tosaid valve chamber for circulating fuel for cooling said nozzle.
 6. Aunit fuel injector having fuel cooling means as set forth in claim 1wherein said nozzle includes a differential valve, a check valve in saidnozzle adjacent said differential valve to increase sensitivity toreturn flow from said differential valve to said high pressure chamber.7. A unit fuel injector having fuel cooling means as set forth in claim1 including a cam driven by said engine, a cam follower operating inresponse to rotation of said cam for operating said plunger, said camdefining a cam lobe for driving said plunger to close said port meansprior to initiation of the power stroke of the engine and open said portmeans substantially at the end of the power stroke.
 8. A unit fuelinjector having a fuel cooling means as set forth in claim 1 including acam, means for driving said cam, a cam follower engaging said cam andconnected to said plunger, said cam driving said cam follower and saidplunger to initiate and terminate fuel injection on the rising portionof said cam with a sufficient dwell for maintaining the port means in aclosed position during the greater portion of the power stroke of thecorresponding cylinder.
 9. A unit fuel injector having a fuel coolingmeans as set forth in claim 1 wherein said plunger includes a pumpingland on said plunger for initiation and termination of fuel injectionupon closing of said inlet port and opening of said return portrespectively, a cam for driving said cam, a cam follower driven by saidcam driving said plunger, said cam defining a lobe for lifting said camfollower and said plunger to maintain the port means in the closedposition for substantially 90* of cam rotation.
 10. A unit fuel injectorhaving a fuel cooling means as set forth in claim 1 wherein said plungerincludes a land defining initiation and termination of fuel injectionupon closing of an inlet port with said high compression chamber andopening of an outlet port with said high pressure chamber, a second landon said plunger defining said port, a cam defining a lobe having a dwellof substantially 70* whereby said cam follower maintains said returnpassage means in a closed position for trapping fuel in saiddifferential valve chamber to prevent blow-back in said differentialchamber.